Glove disconnection, which essentially means he’s not getting any extra pull from his glove side, His arm flies open, needs to work on elbow spiral, Needs to work on getting more drive off back leg, getting a longer stride. and when he releases the ball his foot is opened, so it’s even tougher for him to create Hip-Shoulder separation. I’d guess Low 50s based off this. He seems athletically built, and with a good pitching coach could probably get him at high 50’s with accuracy.

Yes, Look at a pro pitcher and very often at landing they’re feet are in line, minus a select few who are closed like Jake Arrieta, but the consistency is no pitcher will have their feet open at Landing. Really kills velocity. I don’t really have many drill suggestions for this, besides maybe trying to draw a line off the mound from where your son throws, and making sure his landing leg lands on it. Do it a lot till it’s muscle memory.